Montana 500 Tear-down Manual
October 5th 2014
Changes from previous teardown manual are in italics.
The purpose of the post-run tear-down is the ascertain that the top T's have complied with the rules.
If there is non-compliance, the inspectors must then decide (usually by a vote of the
inspectors) if the issue of non-compliance rises to the level that would call
for a penalty. Generally if the inspectors feel that an issue of non-compliance
causes a significant or unfair speed or endurance advantage, it should be put to
a vote of the drivers. The drivers may vote to enforce a penalty, up to and
including disqualification of the car and driver (unless another penalty is
stated in the rules) or, allow the item of contention to stand with stipulation
(such as "don't bring it back next year"), or allow the item without
qualification. Drivers are not required to vote, but the inspectors are. The
inspectors should pick a "lead inspector" to be the group's spokesman and help
direct the inspectors. Any driver may refuse a post-run inspection or to be an
inspector. This would be cause for automatic disqualification.
The run begins with a "courtesy" inspection of the
cars. This inspection is designed to find issues of non-compliance so that the
drivers may make changes to become in compliance. However, even if something was
deemed in compliance at the start, it does not mean that it cannot be declared
out of compliance at the end, although it might mitigate the situation.
The following list is broken into three levels.
Each level increases the severity of the invasion of the car. Level One tests
should be performed before Level Two, and Level Two tests before Level Three.
The top car may be subject to closer scrutiny than the second or third
car, at the discretion of the inspectors. The inspectors may choose to forgo
higher level operations, although they are free to perform all allowed
operations. The top car will be torn down. If it is disqualified,
the next car will be torn down until a qualified car is found. At this time,
removal of any piston in not allowed, although the rod cap may be removed, and
the piston may be slid in the bore, so long as no rings leave the bore. As per
rule E9, the inspectors will ask the the drivers present at the tear down if
there is anything the drivers would like reviewed on any of the
top three car s. The drivers present will then
decide by majority vote on any additional items for the inspection team to look
Ascertain that the fenders are metal and the correct year for the body.
Gas tank must be in original location.
Check lead seals to make sure that they have not been broken nor tampered with.
Check to see that windshield is sealed and in compliance.
Check for substantial pickup box or turtle deck.
Fuel line size must not exceed 3/8"
Check tailpipe for at least 36" of 1-1/2" pipe.
Check timer for correct type.
Remove and check carburetor. Use venturi gauge and throat gauge. (see picture 2.)
Check rear end ratio. Using the valve stem or some other mark on the tire, crank the engine with the
hand-crank, with the car in high gear. Note how many turns of the crank are
required to turn the tire exactly one revolution. The correct number is
3-7/11 (3.63) turns of the starting crank. Incorrect numbers could be
exactly 4 turns, or exactly 3 turns.
Check coils for allowed type. Must be non-electronic with magnetic contact points.
Check ignition switch. Must be original type.
Check for any other visibly out-of-specification parts.
Remove transmission cover. With a mirror, check for shaved flywheel or missing magnets.
Check rear end for non-original type bearings. The outer zerks or grease cups can be removed and a pick
placed into the hole. You should be able to see the rollers. A bore scope
can be threaded into the oil filler hole and up over the axle to see if the
pinion bearing is of the proper kind.
Check to see if Ruckstell is locked into high, if so equipped.
Check for absence of auxiliary brakes.
Check for proper front and rear spring complement. There must be seven leaves, all different sizes from long
on the bottom to short on top.
Check for absence of accessory pan arms.
Check for absence of steering dampener.
Check to see that the battery used for ignition does not exceed six volts.
Check that spray needle exceeds .110" with no go gauge.
Remove and CC cylinder head. One
combustion chamber must be untampered with. The other three may be ground
out to match the standard chamber. Remove a spark plug. Invert the head and
place it on the stand. Fill spark plug hole level full of modeling clay.
Place a thin layer of grease around combustion chamber and place Plexiglas
cover onto this. Fill the bottle with water. The bottle holds 265 CC's when
filled to the brim. Pour this water carefully into the combustion chamber
through the hole in the Plexiglas cover. The combustion chamber must hold
265 CC's of water, plus five more (from a syringe), for a total of 270 CC's.
Check cylinder bore with no-go
Remove manifolds and check
manifold ports. Use no-go side of port gauge. (see picture 1.) Either the
gland ring or manifold port must not pass the gauge.
Look for grinding or polishing of
Remove lower oil pan and check
for modifications to the inside oiling system.
Check to make sure at least one
rod and piston assembly is unmodified.
Check for notches in the cam
bearing bores that would allow oversized lobes.
Check the sweep of the piston.
Should not exceed 4.030" Use 4" standard supplied by club and dial
indicator. (see ill.)
Piston should not protrude more
than .400" above head gasket surface. Use depth gauge.
Check for non-counterweighted
Check valve head diameter. Must
not exceed 1.500"
Remove rod cap and check size of
crank. Must be between 1.208" and 1.250"
Remove a valve. Check stem size.
Must be larger than 5/16" Check to see that seat bore is not relieved. Use
seat bore no-gogauge
Tappet foot must not exceed 1.00"
Carefully push up piston of rod
with removed cap. Do not allow top ring to come out of bore! Distance from
top of top ring to top of piston is XXX A value higher than this would
indicate pistons with an increased compression distance (Egge pistons,
Check to make sure rod center to
center distance is less than 7.030" (see rod length addendum).
The Montana 500 is Sanctioned by
The Montana Cross Country T Association.
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